The present invention relates generally to soil processing tools and a method of using soil processing tools on a larger scale than known in the prior art for modifying the structural integrity of material in a subterranean earth situs. More particularly, the present invention is provided for use in large scale projects where the structural integrity of vast amounts of subterranean soil is to be processed. The invention also provides a method of forming precision soil-cement columns of any diameter by forming a sacrificial guide which centers and guides the soil processing tool.
Soil processing tools have been used in the prior art in building foundation systems, load bearing walls and also for soil modification. Soil modification is a broad concept which includes without limitation the solidification or hardening of various subterranean sites for a variety of purposes. At present, the tools used for underground soil modification are typically between three and five feet in diameter. Attempts to use any large scale soil processing tools, i.e., with diameters greater than about 5 feet, are complicated by the fact that it is difficult to control such large tools and to create perfectly vertical soil cement columns with them. For example, the forming of vertical columns on precise centers is critical if the soil processing project includes the hardening of a large volume of material for supporting an airport runway, or the solidification of a radioactive underground plume.
The present invention provides for the first time a large scale processing tool having a diameter of between 8 and 20 feet (and perhaps larger) but which can be controlled and guided to form precision vertical holes and soil cement columns centered at precise locations. The present invention accomplishes this result in part by the use of one or more preformed sacrificial guides. The preformed sacrificial guide cooperates with a pilot in the much larger soil processing tool to assure that the larger tool remains centered and bores downwardly in essentially a perfectly vertical path. By using the preformed sacrificial guide, large arrays of soil cement columns may be formed in processing large volumes of underground earth sites. In many of these large underground sites, it is critical that the entire volume of the underground site be either solidified into a rather solid soil cement mixture or thoroughly processed to assure a uniform result. For example, for support of an airport runway, the underground material beneath the runway must have uniform strength. As another example, in treating a large underground radioactive plume, it is critical that the entire volume of the plume be solidified or otherwise treated to minimize future movement of the radioactive materials in underground water tables.
The present invention also provides for the first time a method for forming soil-cement columns of any diameter that have very precise verticality and precise centering. This high degree of precision is achieved by using a sacrificial guide to position and guide the soil processing tool.
The present invention contemplates the use of some aspects of my prior patents, including U.S. Pat. Nos. 4,793,740; 4,958,962; 5,396,964; 6,183,166 and 6,241,426, all of which are incorporated by reference as though set forth in full herein.
Portions of those prior patents are utilized in conjunction with the present invention and some significant portions of those prior patents will be described herein as they pertain to the present invention.
The overall concept of the present invention is to first form a sacrificial guide with a soil cement mixture and allow the guide to harden sufficiently to act as a pilot for a larger soil processing tool. The pilot shaft of the larger soil processing tool is centered in and guided by the preformed sacrificial guide as the large processing tool begins moving downwardly. As the soil processing tool moves downwardly, its heavy, rotating teeth break up and fragment the sacrificial guide into soil cement particles so that the soil cement mixture utilized to form the sacrificial guide is eventually interspersed into the much larger soil cement column formed by the large scale processing tool. The result is a precisely placed, large diameter and homogeneous soil cement column. An array of such columns can be placed very accurately in order to solidify or otherwise process very large underground sites.
The sacrificial guide may be either a hollow or a solid cylinder and formed, for example, by the technique taught in my U.S. Pat. No. 6,183,166. If the sacrificial guide is hollow, the pilot of the larger soil processing tool is centered and guided by the hollow sacrificial guide. If the sacrificial guide is a solid cylinder, it has a relatively soft center and a relatively hard outer region. In this embodiment, the larger soil processing tool has a pilot which is tipped with an auger. The auger drills out the soft center of the guide, but is simultaneously centered and guided by the hard, outer region of the guide.
A primary object of the invention is to provide a method for hardening or solidifying large volumes of material located in a subterranean earth situs so that the earth situs may be used to support structures carrying large loads such as airport runways.
Another object of the invention is to provide a method for forming underground soil-cement columns of any diameter wherein the columns are formed by using a sacrificial guide and the resultant columns have a higher degree of verticality and more precise centering than known in the prior art.
A further object is to provide a method of forming underground soil-cement columns utilizing a soil-cement sacrificial guide, wherein the guide becomes broken up and fragmented to form a part of the resultant soil-cement column.
Another object of the invention is to provide a method for forming a sacrificial guide which centers and guides a large diameter soil processing tool having a diameter of more than 8 feet which can be controlled and guided to form precision vertical soil-cement columns centered at precise locations.
A further object is to provide a method for hardening or solidifying large subterranean volumes of material wherein an array of sacrificial guides is formed and those sacrificial guides are used to guide and control large diameter soil processing tools to form soil-cement columns in the situs.
Other objects and advantages of the invention will become apparent from the following description of the drawings wherein: